How to Calculate Daily Water Intake: A Step-by-Step Guide

Updated 5 Oct 2026 in Health & Fitness

A rough guide to daily fluid needs in Singapore's hot, humid climate.

Health numbers are most useful when you track them consistently. A quick calculation turns everyday measurements into something you can act on, whether that is planning meals, training for a run or preparing for a clinic visit.

What you need

• Weight (kg)
• Exercise minutes a day

Step by step

1. Enter the weight (kg).
2. Enter the exercise minutes a day.
3. The results update as you type, or press Calculate.
4. Read the suggested water intake first, then the supporting figures below it.

The formula

About 33 ml per kg of body weight plus 350 ml per 30 minutes of exercise.

Worked example

For example, with these inputs:

• Weight (kg): 65
• Exercise minutes a day: 30

the calculator returns:

• Suggested water intake: 2.50 litres

A second example

Now change the inputs to:

• Weight (kg): 81.25
• Exercise minutes a day: 30

the calculator returns:

• Suggested water intake: 3.03 litres

Practical tips

• Asian BMI cut-offs are lower than WHO's, so a 'normal' international BMI can still mean moderate risk.
• See a healthcare professional before big changes to diet or exercise, especially if you have a medical condition.
• Formulas give estimates for the average person; your doctor can account for your history and body composition.
• Singapore's heat and humidity raise fluid needs, especially when exercising outdoors.

Background

Research has shown that Asians tend to develop conditions such as type 2 diabetes and heart disease at lower body weights than Europeans. That is why the Health Promotion Board recommends lower BMI cut-offs for Singaporeans, with 23 marking the start of moderate risk.

Any health calculator gives a general estimate. If a result worries you, or you are pregnant, managing a chronic condition or planning a big change in diet or exercise, speak to a doctor, polyclinic or dietitian.

Programmes such as the National Steps Challenge and the Healthy 365 app have made tracking activity common. Turning those numbers into distance, pace or calories helps set realistic goals for events like IPPT or a 10 km run.

Related calculations

• Calories Burned Calculator: Estimates calories burned with MET values.
• BMI Calculator (Asian Cut-offs): Singapore's Health Promotion Board uses lower BMI cut-offs for Asians because health risks rise at lower BMIs.
• BMI Calculator (WHO): Calculates BMI with the international WHO categories.
• BMR Calculator: Estimates calories your body burns at rest.

Want to skip the arithmetic? The free Daily Water Intake Calculator does all of this instantly and updates as you type.

Run your own numbers: Daily Water Intake Calculator